Deva N. Pattanayak

Diffraction tomography for biochemical imaging with diffuse-photon density waves

The spatial structure of optically heterogeneous turbid media is probed with diffusive light. Projection images are obtained experimentally by deconvolution of the scattered diffuse-photon density waves on a planar boundary by use of a fast Fourier transform. The method is very fast, permitting object localization and characterization in ~1000 volume-element samples on subsecond computational time scales. The optical properties of slice-shape inhomogeneities are accurately determined.

Algorithms for 3D localization and imaging using near-field diffraction tomography with diffuse light

We introduce two filtering methods for near-field diffuse light diffraction tomography based on the angular spectrum representation. We then combine these filtering techniques with a new method to find the approximate depth of the image heterogeneities. Taken together these ideas improve the fidelity of our projection image reconstructions, provide an interesting three dimensional rendering of the reconstructed volume, and enable us to identify and classify image artifacts that need to be controlled better for tissue applications. The analysis is accomplished using data derived from numerical finite difference simulations with added noise.

Diffuse optical 3D-slice imaging of bounded turbid media using a new integro-differential equation.

A new integro-differential equation for diffuse photon density waves (DPDW) is derived within the diffusion approximation. The new equation applies to inhomogeneous bounded turbid media. Interestingly, it does not contain any terms involving gradients of the light diffusion coefficient. The integro-differential equation for diffusive waves is used to develop a 3D-slice imaging algorithm based the on angular spectrum representation in the parallel plate geometry. The algorithm may be useful for near infrared optical imaging of breast tissue, and is applicable to other diagnostics such as ultrasound and microwave imaging.

Diffraction tomography : Finite media and simultaneous reconstruction of absorption and scattering coefficients

An angular spectrum algorithm is presented for fast, near-field diffraction tomographic imaging with diffuse photon density waves in highly scattering media. A general relation in K-space is derived that connects the spatial variations of the optical properties of heterogeneities to the spatial spectra of the measured scattered diffuse photon density waves. The theory is verified with experimental results. We further describe an approach to reconstruct the absorption and scattering simultaneously. We also present how to incorporate boundary conditions into this angular spectrum algorithm for a turbid medium of finite size, in particular, the slab medium.

Photon density waves imaging with K-space spectrum analysis: clinical studies, background subtraction, and boundary effects

In recent years, a variety of techniques for imaging turbid media such as tissue with diffuse photon density waves (DPDW) have been explored. Most of these methods employ iterative techniques (e.g., ART, SIRT, and conjugate gradient) for image reconstruction, and they are in general computationally intensive. In this paper the authors use a recently developed imaging algorithm based on K-space spectral analysis. This technique is fast and noniterative. In addition to providing information about the position of hidden object(s), accurate optical properties of thin heterogeneities can be obtained when information about their depth is available. The authors believe they report here the first clinical image obtained by K-space spectrum analysis of DPDW measurements. In addition a new method for determining the background optical properties of an imaged sample and the influence of boundary conditions are discussed.